An integrated circuit (IC) can use isolation cells and level shifters to couple different circuit modules together. In an example, an IC includes a first circuit module having a power-up mode and a power-down mode, and a second circuit module that powers up at all time during operation. The operation of the second circuit module depends on, for example, a terminal of the first circuit module. The IC can include an isolation cell that couples the first circuit module and the second circuit module together. Thus, when the first circuit module is in the power-down mode, the isolation cell drives a certain logic value to the second circuit module to avoid malfunction due to an undetermined (floating) state on the terminal of the first circuit module.
The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.